JPS6139864Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a shock absorber used in a suspension system of an automobile or the like.

In general, suspension systems for automobiles support the weight of the vehicle body, buffer the vertical vibration of the wheels caused by uneven road surfaces, etc., and prevent vibrations from being transmitted to the vehicle body. Several vibration damping devices are placed between the vehicle body and the wheels in order to protect the cargo carried by the vehicle and to suppress irregular vibrations from the wheels to improve running stability.

The above-mentioned shock absorbers include suspension springs such as leaf springs, coil springs, torsion bars, rubber springs, and air springs, and hydraulic shocks such as standard shock absorbers, monotube gas-filled shock absorbers (docarbon type), and twin inch tube gas-filled shock absorbers. There are absorbers, but the latter type of hydraulic shock absorber is currently in general use.

However, if the damping force of these suspension springs and hydraulic shock absorbers is lowered in order to improve riding comfort, a feeling of uneasiness during turning and a greater forward leaning (nose, dive) during braking will occur, resulting in poor steering stability performance. On the other hand, if the damping force is increased in order to improve handling, the vehicle body becomes more likely to crack due to uneven road surfaces. The drawback was that the ride comfort deteriorated.

In other words, improving riding comfort and improving steering stability are contradictory to each other, and until now it has been difficult to achieve both.

This is because each shock absorber has a unique damping force, so it cannot respond to and dampen small amplitudes and vibrations, and the damping limit is exceeded for large amplitudes and vibrations. This is because the damping force does not have amplitude dependence or vibration dependence, in which the damping force changes in response to changes in vibration.

The present invention was developed in view of the above-mentioned circumstances, and aims to improve riding comfort and controllability by making it possible to change the damping force in response to changes in the input amplitude and frequency. Therefore, it is an object of the present invention to provide a shock absorber configured to satisfy both of these requirements.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a longitudinal sectional view showing a shingle tube type shock absorber 20 according to the present invention, and this shock absorber 20 has the following features:
A conventional shin-inch tube type in which a rod guide 3 having a communication passage 2 and a base 4 are arranged at both ends of an inner cylinder 5 and an outer cylinder 6, and a movable piston 8 to which a piston rod 7 is fixed is brought into sliding contact with the inner cylinder 5. In the shock absorber 1, a plate 10 and a piston 11 are fixed to the lower end of the piston rod 7 by a washer 12, a nut 13, etc., the piston 11 is provided with a slidable cylinder 14, and the cylinder 14 has a bellows. A diaphragm 15 formed into a cylindrical shape is sandwiched between flat washers 16, 16 from both sides, and fixed with screws 17 or caulking.
Attach the end of the plate 10 to the washer 18 and screw 19.
Or it is tightly fixed by caulking etc.

Here, an oil chamber 21 formed by the diaphragm 15 and the plate 10 is communicated with an upper oil chamber 24 of the movable piston 8 through a port 22 of the piston 11 and a communication passage 23 of the piston rod 7.

On the other hand, the diaphragm 15 and the cylinder 1
A hole is made in the center of each of the holes, and needles 25 are provided inscribed in these holes.
is fixed to the lower part of the piston rod 7 by screwing or the like, and thereby the diaphragm 15
And the cylinder 14 becomes slidable on the outer periphery of the needle 25.

The needle 25 also has a diaphragm 1.
A notch 26 having an arcuate longitudinal section or the like is provided at the sliding center of the diaphragm 15.
The effective area of 6 changes non-linearly.

Further, a port 27 is bored in the cylinder 14, and a dash pot 28 is formed together with the piston 11. Note that 9 in the figure is an oil chamber.

The above-mentioned dart pot 28 and port 27 are used to alleviate the impact input, and the frictional resistance of the oil passing through the port 27 provides a margin for the operating time. Also,
The combination of the rigidity of the diaphragm 15, the mass of the cylinder 14 suspended by the diaphragm 15, and the hole diameter of the port 27 makes it possible to construct a vibration system that resonates at a specific frequency.

The shock absorber 20 configured as described above is used when a small displacement input with a high frequency is periodically applied due to minute irregularities on the road surface, and when a large displacement input such as during steering or braking is applied quasi-statically. The effect is as described below for the case where .

Here, for ease of explanation, the specifications of each part are set as follows.

K _D : Rigidity at the center of the diaphragm δ _D : Displacement at the center of the diaphragm W _D : Load at the center of the diaphragm S _E : Effective opening area of the notch C _p : Damping force generated by the notch δ _p : Stroke of the piston 8 C _p : Damping force generated by the piston 8 Δ _p : Pressure change in the piston upper oil chamber 24 C: Total generated damping force However, since C _p and C _p are generated by oil flows in different paths, the total damping force C is: It is determined by

First, the time when a minute displacement is input will be explained.

The piston 8 is slightly displaced due to minute irregularities on the road surface. Now, when the piston 8 is displaced downward by δ _p and a pressure change Δ _p occurs in the lower oil chamber of the piston, a load W _D is applied to the diaphragm 15 due to this pressure change, and the rigidity K of the diaphragm 15 increases as shown in FIG. A displacement δ _D occurs in inverse proportion to _D.

On the other hand, the relationship between the diaphragm displacement δ _D and the effective opening area S _E of the orifice (notch) 26 is
As shown in the figure, it has nonlinear characteristics.
(This is possible by making the shape of the notch 26 arc-like or the like.) Therefore, when a minute displacement is input, the effective opening area S _E of the orifice 26 is large, and the damping force generated by the orifice due to the pressure in the oil chamber at the bottom of the piston is becomes smaller.

Furthermore, since the input from minute irregularities on the road surface contains many high frequency components of 10 Hz or higher, the resonance frequency of the vibration system consisting of the rigidity K _D of the diaphragm and the mass of the cylinder of the dart pot 28 should be set to around 5 Hz. As a result, the minute displacement of the diaphragm is suppressed, and the effective opening area S of the orifice 29 is reduced.
_E maintains almost the maximum value, and the damping force generated by the orifice becomes minimum, as shown in FIG.

Therefore, as shown in the above equation (1) and FIG. 5, the damping force C generated in response to a minute displacement input due to minute irregularities on the road surface becomes small.

Next, the case of large displacement input will be explained.

When inputting a large displacement such as during steering, it can be considered as an almost static input compared to the input caused by minute irregularities on the road surface.
(The frequency component is only 3 Hz.) Now, when the piston 8 is quietly displaced downward by δ _p and a pressure change Δ _p occurs in the upper oil chamber of the piston, this pressure change causes a load W _D to be applied to the diaphragm 15. In addition, as shown in FIG. 2, a displacement δ _D occurs in inverse proportion to the stiffness K _D of the diaphragm 15.

On the other hand, the relationship between the diaphragm displacement δ _D and the effective opening area S _E of the orifice is as shown in Fig. 3.
Provide nonlinear characteristics. (The shape of the notch 26 is made into an arc shape, etc.) Therefore, when a large displacement is input, the effective opening area of the orifice continues to be slightly reduced due to the displacement of the diaphragm, so the damping force generated at the orifice also increases slightly. The pressure displacement in the lower oil chamber of the piston increases. For this purpose, diaphragm 2
The displacement increases, and the effective opening area S _E of the orifice decreases.

By repeating the above-described cycle, during a large stroke, the effective opening area S _E of the orifice decreases, the orifice generated damping force C _p also increases, and the total generated damping force C increases.

In this case, since the frequency component of the input to the dart pot 28 is low, the resistance generated is small and the influence can be ignored.

Next, regarding frequency dependence, we will talk about the frequency dependence.
8, the frequency component of the input is very high in response to an impactful input such as when crossing a horizontal joint, so the dart pot 28 generates an almost infinite force, causing the displacement of the orifice 15. Forcibly suppress.

Therefore, the effective opening area of the orifice is maintained at approximately the maximum value, and the damping force generated by the orifice becomes extremely small. Therefore, it can be seen that frequency dependence effectively acts on impact input.

As explained above in detail, the shock absorber according to the present invention has a structure in which an orifice and a doss pot are provided in the conventional shingle tube type shock absorber. Since the damping force generated is small, it absorbs vibrations during driving and provides a comfortable ride.Furthermore, the damping force generated by the orifice increases when a large displacement input is applied, resulting in good handling when turning or braking. .

In addition, for low vibration frequencies, the dart pot responds and the diaphragm displaces, and the damping force generated by the orifice becomes small, while for high frequencies, the dart pot hardly displaces, and the damping force generated by the orifice becomes minimum. As a result, the force transmitted from the road surface to the vehicle body due to impact input when passing through a side joint, etc. is reduced, making it possible to achieve both handling stability and ride comfort by providing a good ride with less impact feeling. Become.

[Brief explanation of the drawing]

Figure 1 is a longitudinal sectional view showing the shock absorber of the present invention, and Figure 2 is the load W acting on the diaphragm.
A diagram showing the relationship between _D and the diaphragm displacement δ _D due to this load, Figure 3 is a diagram showing the relationship between the diaphragm displacement δ _D and the effective opening area S _E of the orifice, and Figure 4 is a diagram showing the diaphragm displacement δ _D Figure 5 shows the relationship between the piston speed and the total generated damping force _C , and Figure 6 shows the relationship between the input vibration frequency and the dart pot generated resistance force. It is a diagram. 1...Conventional shock absorber, 2...Communication path, 3...Rod guide, 4...Base, 5...
Inner cylinder, 6... Outer cylinder, 7... Piston rod, 8...
...Movable piston, 9...Oil chamber, 10...Plate, 11...Piston, 12...Washer, 13
... Nut, 14 ... Cylinder, 15 ... Diaphragm, 16 ... Flat washer, 17 ... Screw, 1
8... Washer, 19... Screw, 20... Shock absorber, 21... Oil chamber, 22... Port,
23...Communication path, 24...Upper oil chamber, 25...Needle, 26...Notch, 27...Port, 28
... Datsushiyupot.

Claims (1)

[Scope of utility model registration request] In the shock absorber, a rod guide with a communication passage bored therein and a base are arranged in an inner cylinder and an outer cylinder, and a movable piston with a fixed piston rod is slidably contacted in the inner cylinder, and the piston is attached to the lower end of the piston rod. A cylinder with a hat-shaped diaphragm fixed thereto is provided, and the end of the diaphragm is tightly fixed to the piston, and the oil chamber formed by the diaphragm is connected through a port of the piston and a communication passage of the piston rod. The needle is connected to the upper oil chamber of the movable piston, and a needle having a notch with an arcuate cross section is fixed to the lower part of the piston rod, and a port is drilled in the cylinder, and the piston and cylinder and the port drilled in the cylinder connect the needle pot. A shock absorber characterized by forming a.